Circuit breaker



sept. 15, 1959 Filed Oct. 28, 1954 Fig 2 F. L. GELZHEISER ETAL CIRCUIT BREAKER 5 sheets-Sheet 1 SePt- 15, 1959 F. .GE1 zHElsER ETAL 2,904,655

CIRCUIT BREAKER 3 Sheets-Sheet 2 Filed Oct. 28, 1954 Fig. 4.

Fig.5.

Fig.6.

Sept. 15, 1959 F. L. GELzHElsER ETAL 2,904,655

, v CIRCUIT BREAKER Filed 9ct. 2, 1954 s sheets-sheet s Fig. |27

United States Patent O CIRCUIT BREAKER Francis L. Gelzheiser, Beaver, and Robert H. Flick, Brighton Township, Beaver County, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 28, 1954, Serial No. 465,262

16 Claims. (Cl. 200-88) This invention relates to circuit breakers and more particularly to circuit breakers for controlling lighting and moderate power circuits.

Application Serial No. 664,758, iled June 10, 1957, is a division of this application.

An object of this invention is to provide a circuit breaker embodying an improved thermally and magnetically responsive trip device with improved means for Calibrating the trip device.

Another object of the invention is to provide a circuit breaker having a thermally and magnetically responsive ltrip device with separate means for Calibrating the thermally responsive trip device and the magnetically responsive trip device.

Another object of the invention is to provide a circuit breaker having a two-piece housing of molded insulating material comprising a base and cover, the cover having a slot molded in one end wall thereof for receiving adjusting and mounting screws, without the necessity of drilling, the slot being then lled with a suitable material to prevent tampering and provide insulation.

Another object of the invention is to provide a circuit breaker, a housing of molded insulating material comprising a base and cover, the base having a vent passage formed by two adjoining openings therein, one of said openings being formed from the top of said base and the other from the bottom, said openings adjoining to form a horizontal passage.

Another object of the invention is to provide a circuit breaker embodying a housing in which a separate portion of the housing such as a cover plate is inserted and firmly held in place without being positively fastened to the main part of Ithe housing.

Another object of the invention is to provide a multipole circuit breaker having thermally responsive and magnetically responsive trip means for each pole with separate means for Calibrating the thermally responsive trip means for each pole and a single Calibrating means for Calibrating the magnetically responsive trip means for all of the poles of the breaker.

The invention both as to structure and operation, together with adidtional objects and advantages thereof, will be best understood from the following detailed description thereof when read in conjunction with the accompanying drawings.

In said drawings:

Figure 1 is a vertical sectional view taken substantially on line I--I of Fig. 3 of a circuit breaker embodying the principles of the invention;

Fig. 2 is a vertical sectional View taken substantially on line II-II of Fig. 3;

Fig. 3 is a vertical sectional view taken on line III- HI of Fig. l and looking in the direction indicated by the arrows;

Figs. 4, 5 and 6 are elevational views respectively showing trip members for one, two and three-pole breakers;

Patented Sept. 15, 1959 ICC Fig. 7 is a bottom view of the circuit breaker showing the insertable plate for the housing;

Fig. 8 is a detailed view of the insertable bottom plate;

Fig. 9 is a sectional view of the trip device showing the adjustment for the thermal trip element before the insulating sealing cement is applied;

Fig. 10 is a fragmentary detailed viewY of the calibrating device and biasing spring for the magnetic trip means, and

Fig. 11 is an end elevational view of a part of the cover showing the slot molded therein for receiving the adjusting screw and the mounting screw for securing some of the parts thereto. This View shows the end of the breaker before the insulating cement is applied.

Referring to Fig. 1 of the drawing, the circuit breaker generally comprises a two-piece housing of molded insulating material including a base 11 and cover 13, a stationary contact 15 and movable contact 17 for each pole of the breaker, an operating mechanism 19 and a trip device 21. The housing is divided into two separate compartments by means of matching barriers 23 and 25 molded integral respectively with the base 11 and the cover 13. v

The stationary contacts 15 for each of the two poles of the breaker are mounted on the inner ends of conducting members 27 integral with a plug-in or other terminal connector 29 supported in the base 11 of the housing. The moving contact 17 for each pole is rigidly secured to a U-shaped switch or contact arm 31. Both of the contact arms 31 (Figs. l and 2) are operated to open and closed positions by the operating mechanism 19 to open and close the contacts.

The operating mechanism 19 comprises an operating member 32 having an integral operating lever 33 for each pole of the breaker and a single operating handle 35, an over-center spring 37 for each pole of the breaker and a releasable trip member 39. The operating member 32 including the handle 35 and the operating levers 33 for both poles of the breaker comprises a single member of molded insulating material so that operation of the handle simultaneously moves both of the levers 33. Molded on the operating member 32 is a central bearing surface 41 for pivotally supporting the member in the barrier 25 in the cover 13. Similar bearing surfaces 42 (Fig. l) on the ends of the member 32 are provided for pivotally supporting the ends of the member in the side walls of the cover `13. The barrier 25 is provided with a slot 43 having a semi-circular bearing portion at its upper end for securing and positioning the operating member. After the operating member 32 is inserted in the slot 43, a support and closure member 45 of insulating material `is inserted in the slot and suitably secured thereon. The upper end of the member 45 has a semicircular bearing surface engaging and supporting the bearing portion 41 of the member 32. The end bearing portions 42 of the member 32 are similarly secured and supported in the side walls of the cover 13.

The releasable trip member 39 (Figs. 1 and 2) comprises a spring support lever or trip arm 47 for each of the poles ofy the breaker, each of the spring supports or trip levers being secured adjacent its pivot axis to a tie rod or cross bar 49 of molded insulating material for unitary pivotal movement. The tie rod 49 is provided with a central bearing portion 51 (Fig. 2) for pivotally supporting the releasable trip member 39 in the barrier 25 and with end bearing portions 52 (Fig. l) for supporting theV ends of the'releasable trip member 39 in bearing portions (not shown) in the side walls of the cover 13. The spring support or trip lever 47 for one of the poles lof the breaker extends toward the right (Fig. 1) and has a latch end 53 which is normally engaged and releasably held by a single latch element of the trip device 21 (to be later described) to releasably hold both of the trip arms 47 of the releasable trip member 39 in operative position.

Each of the operating levers 33 is bifurcated and-the spaced legs 55 thereof are provided with notches S7 in which are seated the inner ends of the legs 59 of the U-shaped switch members 31. The switch members 31 are held in place by the over-center operating springs 37 which are connected under tension between the switch members 31 and the corresponding spring supports 47 of the releasable trip member 39. In the position shown in Fig. l the spring 37 biases the switch member 31 to the closed position, and when in open position the spring 37 biases the switch member 31 to the open position.

The circuit breaker is opened manually by moving the operating member 32 (Fig. l) by the handle 35 cloek- Wise from the on to the off position. During this movement the upper ends of the switch arms 31 are carried over to the left of the line of action of the overcenter springs 37 whereupon the springs move the switch arms to the open position with a snap action. The contacts are closed by reverse movement of the operating member 32, that is, from the off to the on position. During this movement the upper ends of the switch members 31 are moved over to the right of the line of action of the overcenter springs which then move the switch members to the closed position with a snap action.

An arc extinguisher 61 for each pole of the breaker may be disposed in openings or arc chambers 60 formed from the top of the base adjacent one end thereof for quickly extinguishing the arc drawn when the circuit is interrupted. The arc extinguishers may be of any suitable type, the one shown comprising a series of spaced, slotted plates of magnetic material into which the arc is drawn and quickly extinguished. The arc gases are drawn into a vent passage 62 along the bottom of the base 11 under a cross barrier 67 and vented out the end of the housing opposite the stationary contacts. The vent passage is formed by the opening 6G formed from the top of the base 11 at the left end thereof and an opening 117 formed from the bottom of the base 11 adjacent the right hand end. These two openings adjoin to form the horizontal passage extending along the bottom of the base. With this arrangement the horizontal vent passage 62 may be molded in the base 11 by two vertically separable mold parts without any drilling or other operation to form the horizontal passage.

The circuit breaker is tripped open automatically in response to overload currents by operation of the trip device 21. A trip device 21 is provided for each pole of the breaker but since the trip devices are alike only one will be described. The trip device comprises a bimetal element 63 having one end rigidly secured to the inner end of a conducting strip 65 with the high expansion side of the bimetal element on the outside of the loop. The conducting terminal strip 65 which is secured by means of a screw 66 t0 the end wall of the cover 13, extends out through an opening in the base 11 below the cover 13 and has a terminal connector 71 at its outer end.

As shown in Figs. l, 2, 9 and l1 the cover 13 has a vertical slot 68 molded in the end wall from the lower edge thereof, for receiving the screw 66 which secures the conducting strip 65 and the magnet yoke 95 to the end wall. The slot 68 is wide enough to receive the shank of the screw, and the head of the screw engages the end wall of the cover on opposite sides of the slot to rigidly secure the parts thereto. An adjusting screw 101, the purpose of which will be later described, also extends through the slot 68 at the upper end thereof. In this manner the slot 68 provides an opening for the adjusting screw 101 and for the retaining screw 66 for rigidly mounting the parts on the end wall of the cover without the necessity of drilling holes therein. After the parts are mounted on the cover and the thermal trip device is calibrated by adjustment of the screw 101, the entire slot 68 is filled with a suitable material such as a cement to prevent tampering with the calibration and to insulate the live parts of the assembly, so that the user will be protected from receiving an electrical shock.

The free end 73 of the bimetal element is conductively connected to the switch member 31 by means of a flexible conductor 75. A movable trip bar 77 (Fig. 5) formed from a single piece of flat sheet insulating material extends across both poles of the breaker to be actuated by the trip device 21 for either pole. The trip bar 77 is supported at its ends in notches 79 formed by projections 81 molded in the base 11 adjacent the sidewalls thereof. The barrier 23 in the base 11 is provided with a V-shaped opening 33 for receiving the trip member 77 which at this point terminates just below the barrier 25 in the cover 13 so that when the cover is in place it will hold the trip member in place by preventing it from moving upwardly. As shown in Fig. 9 the trip member 77 has an opening S5 therein into which extends the angular upper end of a latch member 87 suitably secured to the side of the trip member. The latch member $7 normally engages latch end 53 of the trip arm 47 and restrains the releasable trip member 39 in operative position. A spring 39 (Figs. l and l0) is compressed between a spring seat 90 in a recess in the barrier 23 and the trip member and biases the trip member to its latching position.

in each of the compartments the trip member 77 has an upwardly extending projection 91 which at its upper end has rigidly secured thereto by means of a rivet 92 an armature 93 for cooperating with a U-shaped magnet yoke 9S. The magnet yoke 95 is mounted on the end wall of the cover 13 with the yoke portion thereof disposed between the conducting strip 65 and the end wall and surrounds three sides of the conducting strip 65. The magnet yoke is rigidly secured in place by the screw 66 which also secures the conducting terminal strip and the bimetal and magnet assembly to the end wall of the cover 0f the housing.

Upon the occurrence of an overload current of, for example, up to l000% of normal rated current the bimetal element 63 becomes heated and when heated a predetermined amount bends rearwardly in a direction to close the loop, since the high expansion side is on the outside of the loop, and moves the free end 73 thereof toward the right. This causes the bimetal to engage the rounded head of the rivet 92 and rock the trip member 77 clockwise disengaging the latch member 37 from the releasable trip arm 47 thus releasing the entire trip member 39. As soon as the releasable trip arm 39 is released, the springs 37 for both poles of the breaker rotate the releasable structure 39, including the spring support or trip member 47 for each pole, in a clockwise direction to the position where it is arrested by engagement by the latch end of the spring support or trip arm i7 with a projection 97 on the base 11 of the breaker housing. This movement of the releasable trip member 39 carries the line of action of the springs 37 for both poles of the breaker over to the right of the associated switch members 31 and the springs 37 then move tthe switch meinbers to the open position with a snap action. When the springs 37 move over center, they act through the switch members 31 to move the handle 35 to an indicating position between the on and oil positions, giving a single indication that both poles of the circuit breaker have been tripped open.

Upon the occurrence of a heavy overload current, of, for example, 1000% or more of rated current or a short circuit current, the armature 93 is attracted to the magnet yoke 95, actuating the trip member 77 to disengage the latch 87 to instantaneously trip the breaker. If the circuit has been heavily loaded, but not quite to the point where the bimetal would cause tripping, the bimetals 63 Will be heated and will move the armatures 93 to a position closer to the yokes or pole pieces 95. Under these s Conditions the magnetic trip will take place at a lower value of current than when the circuit has not been heavily loaded. Also, by having the plurality of armatures mounted on the single trip bar, the force of the magnetic attraction is the sum of forces exerted by all the pole pieces, so that magnetic tripping will be faster if several poles are overload rather than just one.

Before theA contacts can be closed following an automatic opening operation, it is necessary to reset and relatch the mechanism. This is accomplished by moving the handle 35 and the operating member 32 to a position slightly beyond the off position. During this movement theY legs 55 of the levers 33 engage pins 86 in the releasable trip members 47 and restore the entire releasable structure 39 for both of the poles to the latched position. The contacts are then closed in the previously described manner by movement of the handle 35 and the levers 33 to the on position.

The position of the movable end of the bimetal and, hence, the thermal tripping time of the trip devices is adjusted by means of screws 101there being a screw 101 for eachy pole of the breaker. The screws 101 threadedly engage upwardly extending portions 103 of the steelV magnet yokes 95 and their rounded inner ends apply a pressurey to the supported legs of the bimetal elements 63 at the point where they are secured to the inner ends of the conducting strips 65. Just below the point of engagement of the screw 101 with the bimetal element the conducting strips 65 are provided with lateral projections 105 (Figs. l, 2 and 3) which are adapted to engage spaced hooked portions 107 formed on the up- Wardly extending projections 103 of the magnetic yoke and extending inwardly therefrom. The point at which the projections 105 engage the hooked portions 107 forms a pivot or point indicated at X about which the upper end of the conducting strip 65 will bend when the screw 101 is turned. As shown in Fig. 9 the screw 101 has been turned slightly clockwise increasing the pressure on the upper end of the conducting strip 65 causing it to bend and bodily displace the bimetal element in a counterclockwise direction about the point X. During this adjustment, the free end 73 of the bimetal moves closer to the rivet 92, reducing the amount of bimetal movement required on heating before the latch end of the releasable trip member 47 will be released by the latch portion 87. Upon counterclockwise rotation of the screw 101 the inherent resiliency of the conducting strip 65 will cause it to move back toward its normal position, thus pivoting the bimetal element 63 about the point X in a clockwise direction.

Means is provided for adjusting the unattracted position of the armature 93 relative to the magnet yoke 95 independently of the adjustment of the bimetal element. This means includes a plurality of notches 109 (Figs. l and l) molded in the center barrier 23 of the base 11 for receiving headed rivets 111 of different lengths. As shown in Fig. lO, the head of a rivet 111 is placed in one of the notches and the body of the rivet extends toward the trip bar 77 slightly to the right of the left hand edge of the V-shaped notch 83 in the barrier 23 of the base 11. The rivet 111 is held in place by the lower edge of the barrier 25 in the cover and provides a stop for the trip bar 77. By varying the length of the rivet 111 or Iby placing a longer rivet in one of the other notches 109, the unattracted position ofthe trip bar 77 may be varied thus varying the position of the armature 93 relative to the magnet yoke 95.

While there has been specifically described a two-pole circuit breaker, the invention may readily be adapted for use in either a single-pole breaker or a three-pole breaker. A single-pole circuit breaker is provided by omitting the left-hand pole unit (Fig. 2) and the parts therein and substituting a` trip member 113 as shown in Fig. 4 for the trip bar 77. A three-pole circuit breaker is provided by adding a pole unit like the pole unit shown in Fig. 2

to the right of the breaker (Fig. 3). The operating member 32 (Fig. l) would be extended to provide an operating lever 33 for the third pole and the releasable trip member 39 is also extended to provide a trip arm 47 for the third pole. In the three-pole breaker the trip bar 77 (Figs. 3 to 5) would be replaced by the trip bar 115 (Fig. 6). The operation of the single-pole and threepole breakers would be the same as that described for the two-pole breaker illustrated.

In molding the (base 11 it has been found advantageous to provide the opening or openings 117 (Figs. 1, 2, 3 and 7) in the bottom wall 69 of the base 11 to permit the passage of a die member in order to mold the vent passage under the cross barrier 67 and the projection 97. After the breaker is assembled it is necessary to close the openings 117 by means that is resistant to internal and external pressure and which is strong mechanically and electrically.

As shown in Figs. l and 2, the base 11 is molded with ledges 121 on the bottom Wall 69 of the base and extending across each compartment of the base.` Ledges 123 are also molded on the bottom wall 69 of the base 11 extending lengthwise of the compartments. Near the center of the side edges of the opening 117, projections 125 are molded on the ledges 123 near the center thereof andof slightly less width than the ledges so that the projections do not extend into the openings 117 as can be seen in Fig. 3.

Plates 127, one of which is shown in Fig. 8, are adapted to be inserted in the openings 117 and locked in place. The plates 127 are made from a suitable insulating material and have notches 129 in the side edges thereof for engaging the projections 125 (Fig. 7) on the base 11. The plates are installed by inserting one end thereof` in the opening 117 so that it rests on the left hand ledge 121. The plate 127 is then bowed slightly and the other end is inserted in the opening 117 so that it rests on the right handledge 121' after which the plate is slid toward the right until the notches 129 register with the projections 125 at which time the plate, due to its resiliency, snaps into place and is locked against removal by engagement of the notches 129 with the projections 125.

'Ihere is provided a circuit breaker embodying a thermally and magnetically responsive trip device wherein the thermally responsive element is rigidly supported on a conducting strip mounted on one end wall of the breaker housing and is pivotally movable by bending the conducting strip about a xed point for purposes of calibration. The magnetically responsive element is calibrated independently of the thermally responsive element by the insertion of stop members of various lengths in recesses provided therefor in the breaker housing. An opening provided in the bottom of the housing for facilitating manufacture thereof with a horizontal vent passage is closed by the insertion of a suitable insulating member which,- when placed in position is automatically locked 1n position.

While the invention has been specifically disclosed in accordance with the provisions of the patent statutes, it is to be. understood that various changes in the structural Adetails and arrangement of parts thereof may be made Without departing from the spirit of the invention.

We claim as our invention: Y

1. A circuit breaker comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, a trip device comprising a bimetal element having means for initiating release of said releasable means, means. supporting said bimetal element at one end, said support means having laterally extending projections thereon, a member disposed along one side of said support means, an adjusting screw on said member for applying a pressure to said support means, and portions of said member extending to the other side of said support means and coacting with said 7 projections to form a pivot about which said support means moves upon the application of pressure.

2. A circuit breaker comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, a conducting strip for connecting said circuit breaker in an electrical circuit, a trip device for initiating release of said releasable means comprising a bimetal element having one end mounted on an end of said conducting strip, electromagnetic means for initiating release of said releasable means including a U-shaped magnet yoke surrounding three sides of said conducting strip and having a portion extending along one side of said conducting strip toward the end thereof on which said bimetal element is mounted, an adjusting screw engaging said portion of said magnet yoke adjacent said conducting strip for applying a pressure to move said conducting strip adjacent the end thereof, and interengaging portions on said magnet yoke and on said conducting strip to form a pivot point about which said bimetal element moves upon a change in the pressure applied by said adjusting screw.

3. A circuit breaker comprising an insulating housing, relatively movable contact means, means releasable to effect automatic opening of said contact means, a conducting strip extending into said housing along one end L wall thereof and having laterally extending projections thereon spaced from the inner end thereof, a trip device for initiating release of said releasable means comprising a bimetal element having one end mounted on the inner end of said conducting strip, a member disposed between said conducting strip and said end wall of said housing and terminating adjacent the inner end of said conducting strip, an adjusting screw on said member for applying a pressure to the inner end of said conducting strip, and hooked portions engaging said projections on said conducting strip providing a point about which the inner end of said conducting member bends upon the application of pressure thereto to vary the position of said bimetal element.

4. A circuit breaker having a housing comprising a base and a cover, relatively movable contacts, means releasable to effect automatic opening of said contacts, a trip member mounted in said base normally engaging and restraining said releasable means, a conducting strip extending into said housing and mounted on one end wall of said cover, said conducting strip having laterally extending projections spaced from the inner end of said strip, a trip device for operating said trip member comprising a bimetal element having one end rigidly mounted on the inner end of said conducting strip and the other end free, electromagnetic means for actuating said trip member including a magnet yoke mounted between said conducting strip and said end wall of said cover, means for applying a pressure to the inner end of said conducting strip, and a portion of said magnet yoke extending between said conducting strip and said end wall, said portion of said magnet yoke having members thereon co-acting with said projections on said conducting strip to form a point about which the inner end of said con ducting strip and said bimetal element are moved upon application of pressure.

5. A multipole circuit breaker having an insulating housing comprising a base and cover, said base and cover having one or more matching barriers forming a plurality of compartments, relatively movable contacts in each compartment, means releasable to effect automatic opening of said contacts, a biased trip member mounted in said base and extending across all of said compartments for initiating release of said releasable means, a trip device in each compartment for actuating said trip member against its bias, and adjusting means disposed in a recess in one of the barriers in said base for adjusting the biased position of said trip member, said adjusting means being held in position by the matching barrier in said cover.

6. A multiple circuit breaker having an insulating housing comprising a base and cover, said base and cover having one or more matching barriers forming a plurality of compartments, relatively movable contacts in each compartment, means releasable to effect automatic opening of said contacts, a biased trip member mounted in ysaid base and extending across all of said compartments for initiating release of said releasable means, a trip device in each compartment for actuating said trip member comprising a bimetal element having one end supported in said cover, adjusting means yfor adjusting the position of said bimetal element, electromagnetic means including an armature for each pole of the breaker mounted on said trip members adjacent said bimetal elements, and another adjusting means disposed in a recess in one of the barriers in said base for adjusting the biased position of said trip member, said adjusting means being held in position by the matching barrier in said cover.

7. In a circuit breaker comprising relatively movable contacts and means releasable to effect `automatic opening of said contacts, an insulating housing comprising a base and a cover, a trip device assembly mounted in said cover adjacent one end wall thereof, means on said trip device assembly for adjusting said trip device, means on said trip device assembly for securing said trip device assembly to said end wall, said end wall having a continuous slot formed therein extending from the bottom edge of said cover, and both said adjusting means and said securing means being positioned in the one said slot.

8. In a circuit breaker comprising relatively movable contacts and means releasable to effect automatic opening of said contacts, an insulating housing comprising a base and a cover, a trip device assembly mounted in said cover adjacent one end wall thereof, means for adjusting said trip device, means for securing said trip device assembly to said end wall, and said end wall having a slot formed therein open at the bottom edge of said cover for receiving both said adjusting means and said securing means, said adjusting means comprising a screw engaging said trip device at its inner end and having its outer end positioned in and of less Width than the upper portion of said slot adjacent thereto, and said securing means comprising a fastening member also positioned in said slot and having a head of greater width than portions of the slot adjacent thereto so as to engage the edges thereof, and said slot being filled adjacent said adjusting screw with a sealing compound to prevent tampering.

9. ln a circuit breaker, an insulating housing comprising a base and a cover, relatively movable contacts, means releasable to effect automatic opening of said contacts, a conducting strip exending into said housing along one end wall of said cover, fastening means on said conducting strip for securing said conducting strip to said end wall, a trip dev-ice for initiating release of said releasable means comprising a bimetal element having one end mounted on the inner end of said conducting strip, adjusting means on said trip device for adjusting said bimetal element, said end wall of said cover having a single slot formed therein open at the bottom edge of said cover for receiving both said fastening means and said adjusting means.

l0. In a circuit breaker comprising a housing of molded insulating material including a base and a cover, said cover comprising a top portion having a handle opening therein and side and end walls extending downwardly from the top portion to engage the base at a juncture extending generally parallel to said top portion of the cover, said cover having a single slot molded in one end wall thereof and extending `up from the bottom edge of said cover in the direction toward said top portion thereof, a trip device assembly mounted in said cover on said end wall adjacent said slot, adjusting means in the upper portion of said slot, and fastening means extending through the lower portion of said slot for rigidly securing said trip device assembly to the end wall of said cover, said adjusting means and said securing means both being mounted on said trip device assembly.

11. In a multi-pole circuit breaker comprising a housing of molded insulating material including a base and a cover, said cover having a single slot for each pole molded in one end wall thereof, said slots being spaced laterally from each other across the end of the cover with a barrier portion on the cover between adjacent slots and each slot extending upwardly from the bottom edge of said cover, a trip device assembly mounted in said cover on said end wall adjacent each said slot on opposite sides of the barrier portion on the cover, fastening means extending through each said slot for rigidly securing each said trip device assembly to the end wall of said cover, a calibrating screw for the trip device for each pole in the upper portion of each slot, and each said slot being tilled adjacent the calibrating screw with a sealing compound to prevent tampering.

12. A multipole circuit breaker having an vinsulating housing comprising a base and cover, said base and cover having one or more matching barriers forming a plurality of compartments, relatively movable contacts in each compartment, means releasable to elect automatic opening of said contacts, a biased trip member mounted in said base and extending across all of said compartments for initiating release of said releasable means, a trip device in each compartment for actuating said trip member against its bias, each said trip device including a bimetal element mounted at one end in the cover and having its other end extending downwardly toward the base, said biased trip member being pivoted adjacent its lower end on the base and having portions extending upwardly to be actuated by said bimetal elements, a plurality of armatures xedly secured to said biased trip member, a pole piece for attracting each armature, and a stop having a position independent of the bimetal element limiting the position to which the trip member and the armatures thereon may be moved away from the pole pieces by the bias on the trip member.

13. A multipole circuit breaker having an insulating housing comprising a base and cover, said base and cover having one or more matching barriers forming a plurality of compartments, relatively movable contacts in each compartment, means releasable to elect automatic opening of said contacts, a biased trip member mounted in said base and extending across all of said compartments for initiating release of said releasable means, a trip device in each compartment for actuating said trip member against its bias, each said trip device including a bimetal element mounted at one end in the cover and having its other end extending downwardly toward the base, said biased trip member being pivoted adjacent its lower end on the base and having portions extending upwardly to be actuated by said bimetal elements, a plurality of armatures fixedly secured to said biased trip member and movable in unison at all times, a pole piece for attracting each armature, and each of said armatures being moved closer to its pole piece whenever said biased trip member is moved against its bias by any one of the armatures or bimetal elements.

14. In a circuit breaker, two cooperating housing members of insulating material, one of said housing members having a base portion with upstanding side and end walls, the other of said housing members having a top portion with a handle opening therein and depending side and end walls engaging the first said housing member, circuit breaker mechanism enclosed by said housing members and having an operating member with a handle portion extending through said handle opening, said operating member having its plane of movement generally normal to the juncture between the two housing members, a slot molded in the end of one of said housing members from the edge thereof, a terminal strip entering the housing adjacent the end of said slot and extending along said slot `at the inside of Ithe end wall of the housing member, an electroresponsive yelement mounted on said terminal strip inside the housing, a fastening member in the slot and having a head engaging the edges of the slot and mounting the terminal strip on the end wall of the housing, and an adjusting member also in the same slot for Calibrating the electroresponsive element.

l5. In a multi-pole circuit breaker, two cooperating housing members of insulating material, one of said housing members having a -base portion with upstanding side and end walls, the other of said housing members having a top portion with a handle opening therein and depending side and end walls engaging the first said housing member, circuit breaker mechanism enclosed -by said housing members and having an operating member with a handle portion extending -through said handle opening, said operating member having its plane of movement generally normal to the juncture between the two housing members, a plurality of spaced slots molded in the end of one of said housing members from the edge thereof, a plurality of conducting members entering the housing between the two members thereof, each conducting member entering the housing 4adjacent the open end of one of the slots and extending along the inside of the end wall of the housing member at its said slot, an electroresponsive member mounted on each of said conducting members inside the housing for tripping the mechanism, a fastening member in each slot with a head of greater width `than the slot to engage the edges of the slot and mount one of the conducting members on the end wall of the housing, and a `Calibrating screw also in each slot for fixing the tripping point of one of the electroresponsive members.

16. A circuit breaker comprising relatively movable contact means and means releasable to elfect automatic opening of said contact means, a trip device comprising a bimetal element having a portion movable for initiating release of said releasable means, means supporting said bimetal element at one end, a separate member disposed along one side of said support means, an adjusting screw in said separate member for applying a pressure to move the end of the bimetal element adjacent said support means, and portions of said separate member interengaging with said support means to form a pivot about which said support means moves upon the application of pressure by said adjusting screw.

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